class Solution
{
public:
    int climbStairs(int n)
    {
        if (n == 1)
        {
            return 1;
        }
        vector<int> dp(n);
        dp[n - 1] = 1;
        dp[n - 2] = 2;
        for (int i = n - 3; i >= 0; --i)
        {
            dp[i] = dp[i + 1] + dp[i + 2];
        }
        return dp[0];
    }
};